Alloxan and dialuric acid; their stabilities and ultraviolet absorption spectra.

It was the purpose of this investigation to determine the ultraviolet absorption spectra of alloxan and dialuric acid. Previous investigators (l-3) reported that these substances had absorption spectra without definite maxima. However, since preliminary studies indicated that maxima were present under certain conditions, it was thought that a more careful investigation should be made. Although Dixon and Zerfas (4) reviewed the literature and concluded that alloxan was stable at p1-I 7.0, others (5-S) found alloxan to be unstable in neutral and alkaline solutions. Since alloxan decomposed as a first order reaction (9), its absorption spectrum was measured by a determination of the decomposition rate and extrapolation to zero time. Dialuric acid was reported to be unstable in acid as well as in alkaline solutions, because of its ease of oxidation by dissolved air (1, 7, 8). Since dialuric acid was prepared by the reduction of alloxan with cysteine (6), oxidation of dialuric acid by air was prevented by the addition of cysteine, and the ultraviolet absorption spectrum thus determined. Inasmuch as the ultraviolet absorption of cysteine was low (9), this did not interfere in the measurements.